Efficient Expression of the Broad-spectrum Antiviral Protein PA in Escherichia coli by Using Structural Optimization of the Translation Initiation Region
Escherichia coli is an important bioengineering host system,and about 1/3 of the marketed protein-based biotech drugs are produced by E.coli.However,many factors such as low expression levels of target proteins due to codon bias and the lack of partial post-translational modifications in eukaryotes limit the widespread use of the E.coli system.The broad-spectrum anti-viral protein is of great significance for the effective prevention and control of outbreaks of emerging and re-emerging infectious diseases similar to the new corona virus.In order to achieve the efficient expression of the broad-spectrum anti-virus protein PA in E.coli and expand its potential clinical applications,the expression level of PA in E.coli was studied by codon optimization and prediction of the minimum free energy(MFE)of the secondary structure of the translation initiation region(TIR)of the mRNA.The results showed that codon optimization can partially achieve high expression of PA in E.coli,but the overall expression level was not very satisfactory.We found that the MFE value of the TIR's secondary structure of the TIR of our chosen window is closely positively related to the level of expression.Synonymous mutation of codons can alter the local secondary structure of TIR and the value of MFE,which can be further used to increase or decrease the expression level of PA.From both positive and negative aspects,it is confirmed that the global codon optimization combined with local adaptation of the MFE value of TIR driven by the local secondary structure of TIR is a realistic and effective strategy to achieve the efficient expression of PA in E.coli.This approach has important application value for the large-scale production of protein biotech drugs in the prokaryotic system.
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